Radiation damage buildup and dislocation evolution in Ni and equiatomic multicomponent Ni-based alloys

Abstract

Single-phase multicomponent alloys of equal atomic concentrations ("equiatomic") have proven to exhibit promising mechanical and corrosion resistance properties, that are sought after in materials intended for use in hazardous environments like next-generation nuclear reactors. In this article, we investigate the damage production and dislocation mobility by simulating irradiation of elemental Ni and the alloys NiCo, NiCoCr, NiCoFe and NiFe, to assess the effect of elemental composition. We compare the defect production and the evolution of dislocation networks in the simulation cells of two different sizes, for all five studied alloys. We find that the trends in defect evolution are in good agreement between the different cell sizes. The damage is generally reduced with increased alloy complexity, and the dislocation evolution is specific to each material, depending on its complexity. We show that increasing complexity of the alloys does not always lead to decreased susceptibility to damage accumulation under irradiation. We show that, for instance, NiCo alloy behaves very similarly to Ni, while presence of Fe or Cr in the alloy even as a third component reduces the saturated level of damage substantially. Moreover, we linked the defect evolution with the dislocation transformations in the alloys. Sudden drops in defect number and large defect fluctuations from the continuous irradiation can be explained from the dislocation activity.

On the role of heterogeneity in concentrated solid-solution alloys in enhancing their irradiation resistance

“…This result is consistent with previous simulations using the same potential [10]. On the other hand, the difference in the defect number from the Zhou potential is small in the considered alloys, which is also observed in previous studies [21]. Based on the Bonny potential, the defect evolution in Ni 0.5 Fe 0.5 and Ni 0.8 Cr 0.2 is similar, whereas Ni 0.4 Fe 0.4 Cr 0.2 shows the lowest defect number after 600 cascade simulations.…”

“…In this study, we have adopted two independently developed EAM potentials to minimize the uncertainty. In fact, these two potentials have both been used to simulate the irradiation response of different CSAs, and the obtained results are consistent with experiments [8,21,24].…”

“…Figure 5 indicates that the velocity of the dislocation first increases linearly with increasing applied stress, thus a slope can be defined from the velocity-stress curve. Previous studies suggest that defect accumulation in CSAs is well correlated with this slope [21].…”

“…However, the original version of the Cr potential leads to instabilities in alloys, and slight modification was made based on the analysis of Anand et al [30]. These potentials have been successfully used to model damage evolution in corresponding alloys previously [8,10,21,24,25].…”

Radiation damage buildup by athermal defect reactions in nickel and concentrated nickel alloys

“…To illustrate the dose accumulation, exemplary snapshots of defect structures corresponding to different irradiation doses (∼ 0.15, 0.25, 0.05 and 0.01 dpa) in Ni are shown in the insets of Figure 1 and the defect structures at the final dose of 0.25 dpa in NiFe and NiCoCr are shown in Figure 2. In the three different samples investigated, we observe different evolution of defect structures in our MD simulations [11,42,43]. At the beginning of the irradiation, point defects and small clusters are created and the amount of defects is linearly increasing [11,42].…”